JPS5999855A - Time division optical exchange - Google Patents

Abstract

PURPOSE:To obtain a high optical output level by applying write/readout to an optical bistable element in response to periodic and exchange information so as to set optionally the length of an exchange frame period, allowing to attain miniaturization of the exchange. CONSTITUTION:A time division optical signal 100 is applied to an optical write switch S120 via a waveguide 110, selected by each time slot and led to any incident terminal of optical bistable elements 130-160. A bias light is injected to the incident terminal of each element via S132, 142, 152, 162. All elements 130- 160 have hysteresis characteristics and when the bias light is applied to the incident terminal, the emitted amount of light has two stable points. The output of each element is transmitted to the waveguide 180 as a time division optical signal 190 via a readout optical switch 170.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switch that performs exchange control of time-division optical signals.

Optical communication systems using optical fibers as transmission paths are capable of high-speed, large-capacity signal transmission, and various transmission methods have been put into practical use. In particular, the time-division transmission method for digital signals that takes advantage of high speed is an important method (/31).In optical communication systems that are currently in practical use, optical signals are The exchange of signals is simply an electrical signal that is transmitted.
After this conversion, 0 is performed. As mentioned above, in the method of converting an optical signal into an electrical signal and exchanging it, when the exchanged signal is transmitted again, the electrical signal is converted into an optical 4W signal.
Since it is necessary to convert to a code and IS, the device becomes complicated and the cost becomes high. Another disadvantage is that it is difficult to exchange high-speed signals of 100 megabits or more than 7 seconds with conventional time-division switching equipment for electrical signals.As a means to solve the above-mentioned disadvantage, we have developed an optical system that exchanges time-division optical signals as optical signals. Switchboards are being studied. Such an optical switch uses a patent application publication gazette as a delay line.

In other words, one word of time-division light is passed through an optical fiber transmission line of a different length for each time slot using an optical switch, and time-division exchange is performed. However, in optical switching equipment that uses such optical fiber delay lines, the delay time is determined by the length of the optical fiber, and the delay time is determined by the length of the optical fiber.
In order to exchange signals with one frame period, a long optical fiber is required, which has the disadvantage of increasing the size of the device. In addition, since time division switching is performed simply by selecting the delay time of the optical transmission path, losses occur at the connection between the optical switch and the optical fiber, and the input optical signal level (compared to the output optical signal However, the purpose of the present invention is to eliminate the drawbacks of the conventional time-division optical signal exchanger described above, and to make it possible to set the length of the frame period to be exchanged arbitrarily, thereby reducing the size of the device. It is possible to provide a time-division optical switch that is easy to use and allows high output optical signal levels to be easily obtained.

According to the present invention, there is a control circuit between the input optical waveguide for inputting the first time-division multiplexed optical signal and the output optical waveguide for outputting the second time-division multiplexed optical signal. V, on a plurality of optical bistable elements into which bias light is injected, the input optical waveguide is connected to the plurality of optical bistable elements in a time slot kl selected by the control circuit of the first time division multiplexed optical signal. a first optical switch circuit connected to the input terminal of the optical bistable element selected by the control circuit of the element;
The control circuit of the second time-division multiplexed optical signal L, and the control circuit of the plurality of optical bistable elements (therefore, the output of one selected optical bistable element) in the selected time slot l. A second optical switch circuit whose end is connected to the output optical waveguide and the control circuit determine in advance the bias light of three optical bistable elements selected in front of the plurality of optical bistable elements by the control circuit. Further, according to the present invention, an input optical waveguide for inputting the first time-division multiplexed optical signal is provided. Outputs the time division multiplexed optical signal of @2
A control circuit and a plurality of optical bistable elements are connected between the control circuit and the output optical waveguide for the optical bistable elements, and bias light is guided between each of the input terminals of the plurality of optical bistable elements. ! , selected by the control circuit of the first time-division multiplexed optical signal.
Here, the control circuit I of the plurality of optical bistable elements switches the bias light guided to the input 1'111 of the selected optical bistable element to the first time division multiplexed optical signal. an optical switch circuit and the control circuit 'r &
1. A time-division optical switching device is obtained, characterized in that a second optical switch circuit connecting the output end of the optical bistable z-wavelength to the output optical waveguide is arranged in the control circuit f. It will be done.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a T-diagram showing one embodiment of the hour/minute IJ optical intersection according to the present invention. In the f41 diagram, the first time-division optical signal 1 (10) consisting of four time slots each carrying different information is transmitted through the input optical waveguide 110 and is selected for each time slot by the optical switch 1201 for writing. It is guided to the input end of one of the four optical bistable elements 130, 140, 150, 160 through the wave path 135.145.155.165. Bias light is further injected into the ends through optical transmission lines 131, 141, 151, 161, optical switch elements 132, 142%, 152, 162 and optical transmission lines 134, 144° 154, 164%, respectively.

Here, the optical switch Reiko 132, 142.152.162
For example, a waveguide type optical switch described on page 309 of "New Edition Optical Fiber Communication" (published by Dentsu-Tsu News Co., Ltd.) can be used.

Optical bistable element 13 (1, 14 (1,150, IGO) all output light tI'outc'J for input light tri11
The characteristics are bistable as shown in FIG.

That is, when the incident light @ P i n is increased from 0 (ζ is Pa, the output light 11Pout increases rapidly,
Conversely, when decreasing from Pin'E-Pt, f shows the output light 11Pout and the light '1. When Pb bias light is added, the output light ffPout=Po * and P, 2
It has two stable points. In addition, in this embodiment, the first
．． 0) Time division optical signal 1000-)% l timeslot A
,B%C.

Each D is a 1-bit U digital number (), and "(
The light intensity of the 1" signal is 0, and the light of "1"1' is greater than or equal to TPt-Pb shown in FIG. These are input terminals 133.1 of the readout optical switch 170, respectively.
43, 153, and 163 are connected, and the output terminal of the outgoing optical switch 17 () is connected to the 0-output optical waveguide 180I, through which the 2nd υ time-division optical signal 190 consisting of four time slots is transmitted. , 2nd tar I4
Each tights and slot of split light No. 44 19 () (each optical bistable element 130.140.150.16002
G) A reading optical switch] 7 (Constructed so that any one output is selected and output by eye) A.1.

Embodiment 1 shown in FIG. 1f shows the fourth, second, third, and
First time slot information D1B.

C and A are respectively n, the first of the second time-division optical signal 7.90
th, 2nd@th, 3rd, and 4th time slot lc [extracted. That is, the second time-division optical signal 19
0, information A and D of the first time-division optical signal 100 are being exchanged. Next, the details of the operation of this embodiment will be explained.〇The optical bistable elements 130, 140, 150, . . . shown in FIG.
1601 are optical transmission lines 131.141115 respectively]
, 161, optical switch element 132.142.152.1
62 and optical transmission line 134.144.154.164,
A bias light of 1 pb is constantly applied through the light.

Here, writing of the first time-division optical signal 1 (10) to the optical bistable elements 130, 140, 150, and 160 is performed as follows.
In the first period in the first evening time slot of 11, first, a control circuit (not shown) detours the optical switch element 132 if- to remove the bias light and closes it again. Therefore, even if the output light amount P is maintained before the optical bistable element 130 is cleared, the output light amount Pout becomes Pa.Next, in the first period in the first time slot, the output light amount Pout becomes Pa. In the period <@2, the writing optical switch 120 causes the λ waveguide 11 to
11 to the input end of the optical bistable element 130, and then disconnect it again. Here, if the first time slot information A of the first time-division optical signal 100 is "0", the incident light 11Pin of the optical bistable element 130 is only the bias light tPb given through the optical transmission line 134, and the output beam of light
holds l) o. -If time slot information A is 61", the total amount of incident light is bias light tpb and signal light t.
Since the sum of pt-pb is Ptl, the optical bistable element 130
After the output light amount Pout is separated from the input optical waveguide 110, the output light amount Pout is maintained at the light amount PL.

Thus, the first time-division optical signal I T'l fl
Each time slot information A%B, C, D is sequentially optical bistable element 130.140%ll50,1601! -% loaded 0-light bistable element 130.140, 150.16 (l
to the second time-division optical signal -1) 19 (+) The output ends of the optical bistable cables 130.14() and 150.160 are output according to the order specified by a control circuit (not shown). The connection to the optical waveguide 180 is performed by ε.In the example shown in FIG. 1j is +7.-ξReikomeanshiZ 'A completedt6o
, 140.15 (), 130's 1S (・ welfare 1), B, C
, Al151 disease was detected and as a result, the first time control light 15
No. in.

υ2) The exchange of information A and 1) is carried out. Here, the light output operation is the above; AI, i2υ in each dime slot.
ノ Period 1i11 i This reading: 3rd period

Figure 1 φ shows 8: result) Usually f, here, the length of the complaint cycle for the uniform that is replaced n! Light switch for JF loading and 5 loop output U) 94! lII! It can be set arbitrarily by l'l, and since it does not use optical fibers of I length and U length as in the case of the reciprocating method, it is easy to reduce the size of the charge by 2+5. Furthermore, by using an optical bistable element with a low level of output light, it is possible to increase the amount of light from the second time-division dimming signal 190 even more than from the first time-division optical signal 100.

FIG. 3 (al, cb+ is a T diagram showing fl, l of a redundant bistable element that can be used in the present invention.

The 38 yen 1tal is an optical bistable element that uses a directional coupling type optical switch. The ability to obtain input and output light characteristics such as IyJ (/) 1
can.

In Fig. 3, tal-Cio is a directional coupling type optical switch, 11i, l: semi-transparent mirror, 12i is a photodetector, 1:
3 is a voltage amplifier. Details of the operating principle 1 are given in the literature I.
E [F] E ψ E, 2-cho-Naruobkantha Artificial Gutronics, K-E Volume 14 (IEFJ Journ
alof Quantum t(electroni
(sx vol-(JJ-14) page 577-5
The sword is mentioned on page 80 (131i;
■ Small bistable conductor laser. By providing a part of the semiconductor laser V-oscillator with a BT saturation absorption part and a part where no true current is injected, J:, lr, J: =, the injection current vs. optical output characteristic and the bistable characteristic. In the first place, it is possible to do this, and at this time, the injected current i is adjusted to an appropriate value ζ).As a result, the incident and output light characteristics shown in FIG. 2 are distorted by 1. Details of the above-mentioned stable conductor laser can be found in the literature Electronics.
Letter (Electronic@Letter) Volume 17, page 741 and 1988 Institute of Electronics and Communication Engineers Optical 1
It is stated in the collection of lecture papers at the National Conference on Waves (Volume 2), No. 272.

FIG. 4 is a diagram showing a second embodiment of the time division optical switch according to the present invention. In Figure 4, the same numbers as in Figure 1 indicate the same components as in Figure 1.
In the embodiment shown in FIG. 41, the optical waveguide 134 for No. 4 circle is used.
The output ends of the optical waveguides 144, 154, 164 and the bias light waveguide 135, 145, 155, 165 are both guided directly to the input end of the optical bistable element 130, 140, 150, 160, as shown in Fig. 4 f. In the embodiment f shown here, the bias light on the optical waveguides 134, 144, 154, 164 is transmitted to the four optical insertion circuits 430, 440, 450, .
4601 thus optical waveguide 135.145.155.1
After the 1Δ light beam of 165-L is combined, the 1 light bistable element 130°140.150.160 is guided to the ITJ input end.

FIG. 5 is a T diagram showing a third embodiment of a time-division optical switch according to the present invention. This embodiment includes four write 2×2 optical switches 210.220% 230°240.4 optical bistable elements 212, 222.232.242, and four read 2×2 optical switches 214.224.234.2.
44. 2x2 optical switch 2 for writing
1″ of each input terminal of 10°220, 230, 240) is an optical waveguide 211 for inputting bias light.
221.231% 24 llC son 41 LAil connected rbr: 1, one of each output terminal is the optical waveguide 213.223.233 that leads to the respective input end ic of the glossy bistable element f212.222, 232, 242 .24
3 are connected to each other. In addition, the above writing 2 x 2
The other input/output terminals of the optical switch (the output terminal 217 of the j1 optical switch 210 and the input terminal 226 of the optical switch 220,
Output terminal 227 of optical switch F220 and optical switch 23
0 input terminal 236, optical switch 230 output terminal 23
7 and an input terminal 246 of an optical switch 240 are connected to each other, and the remaining input terminals of the optical switch 210 are connected to an optical waveguide 250 for inputting the first time-division optical signal (optical switch 2400). The remaining output terminals 260 are open.

In addition, a 2X2 optical switch for reading 214.224.23
One of the input terminals of each of 4.244 is the output end ζ of each n of optical bistable elements 212.222.232.242.
The optical waveguides 215, 225, 235, and 245 guided by the
510, 520, 5311, and 540 are all open. Other input/output terminals include an output terminal of optical switch 214, an input terminal of optical switch 224, an output terminal of optical switch 224, an input terminal of optical switch 234, and an input terminal of optical switch 224.
The output terminals of the optical switch 214 are connected to the input terminals of the optical switch 244, the remaining input terminals 270 of the optical switch 214 are open, and the remaining output terminals of the optical switch 244 are connected to the optical waveguide 280 of the second time-division optical signal. It is connected to the.

The operation of this embodiment will be explained below.0 In this embodiment, the optical switch for writing 2111.220% 230,24
0 and readout optical switches 214, 224, 234,
244 is a control (not shown) when the voltage applied to the pole is 0, fc is in the cross state sV, and (
In each optical switch for writing, the optical waveguides 211, 213, 221, 223, 231, . ! ::233.24
1 and 243 are connected to each other, and the optical waveguide 250
, the output terminal 217 and the input terminal 226 can be connected,
Each party switch for readout (in this case, the leading waveguide 215
．． 225, 235, 245 and respectively tLO) The open output terminals 510, 520, 530, 540 of the original switch are connected, and the input terminal 270 and output terminal 219, the input terminal 228 and output terminal 229, and the input terminal 238 and output This refers to a state in which the terminal 239, the input terminal 248, and the optical waveguide 280 are connected in n-connections. In addition, the through state is a state in which the input/output connection state of the above-mentioned cross state is switched, for example, the writing optical switch 2201 is connected to the optical waveguide 2.
21 and output terminal 227, input terminal 22G and optical waveguide 22
3 is connected. As an optical switch with the above characteristics, for example, lithium niobate crystal 1
'CTi A directional coupling type optical switch configured by providing a diffused optical waveguide or the like can be used. Optical bistable element 21
2.222.232.242 shall all have the input and output light characteristics shown in FIG. 2. In FIG.
234 and 244 are always kept in a crossed state under the control of a control circuit (not shown). As a result, the input ends tc of the optical bistable elements 212, 222, 232, and 242 are connected to the optical waveguides 211, 221, and 231.2, respectively.
41, optical switches 21 [), 220, 230, 240 and optical waveguides 213.223.233.243 to which bias light is applied, and optical bistable elements 212.222
．． 232 and 242 each hold the data previously loaded. - Edge bistable element 212.222
．． The optical waveguide 21 connected to the output end of 232 and 242
5.225.235.245C All optical switch 2
14.224.234.2441 thus optical waveguide 28
It is separated from 0.

FIG. 6 is a time chart for explaining a particular writing and reading operation 7i of the optical bistable element 242 among the operations of the embodiment shown in FIG. Refer to FIG. 6. If Tn is input to the optical switch 240 shown in FIG.
-1=first Cl) time-division optical signal FIG. 6 fat is added. Figure 6 (all the fire reports A, B, C
%D is composed of a 1-bit digital signal, respectively. In the third embodiment shown in Fig. 5, which shows an example using No. 3 as the number, Fig. 1%fX4 (
Unlike the first, K:, and second embodiments shown above, the signal "l"
2, the optical waveguide 2411 connected to the input end of the tip switch 240 always has the optical tube shown in FIG. 2.
A bias light beam shown in FIG. 6(e) is added. When a control circuit (not shown) is applied to a control circuit I (not shown), a control voltage (dl) is applied to a control electrode (not shown) of the optical switch 240 in FIG.

During the period when the voltage applied to the input end 246 is 0, the optical bistable element 242 is connected to the optical waveguide 241, and as a result, the optical bistable element 242 u) is connected to the input end 246 as shown in FIG.
You will get the Mitsujogo. Here, the time during which the voltage N4 is applied is shorter than the pulse width of the optical signal. The amount of light emitted from the optical bistable element 242 (fl is the incident light!) When tel reaches Pi in FIG. Light ll Figure 6 t
When el becomes OI, it becomes Po, and thereafter the output light tPo is maintained as long as the bias light tPb is applied. In this way, the first time-division signal (Fig. 6) (information A of ml is
◎Similarly, control circuits (not shown) N it 2 , 'M
3s 4th time slot) Sequentially turn the optical switches 230, 220, 210 into the n-through state at C.
Optical bistable element 232.222.2121 by
This information B%am'<, -D is written. - The control circuit (not shown) is an optical switch 244U) that connects the It'l control electrode (not shown) with the second time-division optical signal (Fig. 6).
Figure 6 (add gl〇This makes optical bistable element 2
The output end of 42 is guided to the optical guide 280I only during the period when the control voltage fR6 (fgl) is the voltage ■□, and the leading waveguide 280
Second time division 1'Pl 3' in Figure 6 (1) above! ! i
The second time slot 1 is the time-division optical signal 1116 of @1.
The optical signal (tt+) corresponding to the information Al in FIG.
In the time-division optical signal of FIG.
．． 214 into the through state, the information B, A, held in the optical bistable elements 232, 242, 212,
Read out D. In the second time-division optical exchanger thus obtained in the leading waveguide 280, information A and C of the first time-division optical signal (al) are exchanged.

FIG. 7 is a diagram showing a fourth embodiment of the time division optical switch according to the present invention. In Figure 7, the same numbers as in Figure 5 are given the same configuration as in Figure 5! ! Indicates the accumulation. Optical waveguide 2
The first time-division optical signal on 50 is divided into four by the optical branching circuit 700 and then sent to each optical switch 210, 220, 23.
It is guided to the -1 input end of 0,240. Further, bias light is applied to the other input ends f of the optical switches 210.22G and 230.240 by optical waveguides 211, 221, and 231.241, respectively. Light switch 210.
220, 230, and 240 are controlled to be in a cross state at all times, thereby making the optical bistable element 212.2
22, 232, and 242 are respectively applied with L bias light. Writing and reading of time-division optical signals of the optical bistable device are performed using optical switches 210 and 220, respectively.
．． 230.240 and optical switch 214.224.2
This is done by putting 34.244 into the through state. Is the optical signal read out by the optical switch 214, 224, 234, 244 an optical insertion circuit? 60 and then sent out as a time-division optical signal of the leading waveguide 2801C@2.

As described above, according to the present invention, it is possible to arbitrarily set the length of the string to be replaced, and the present invention is not limited to the above-mentioned embodiment. i'i not.

For example, as shown in FIGS. 1, 4, 5, and 7, in this embodiment, the optical bistable element is periodically programmed and read out and exchanged according to the information to be exchanged. As shown, exactly the same conversion operation can be obtained by reading data into the optical bistable element according to the information to be exchanged, and reading it out periodically.

In addition, in the case of a time-division multiplexed optical signal in which one time slot is composed of n bits (n-2), the difference between one optical bistable element shown in this embodiment and n optical bistable elements is The configuration is such that writing and reading of n optical bistable elements is performed 8111 times within a time slot, thereby making it possible to exchange information between time slots.

[Brief explanation of the drawing]

1st flash, FIG. 3 is a diagram for explaining FIG. In Figure 1, 1211.210.220
．． 230, 24 (+ is a write switch, 170.
214.224, 234.244 are readout optical switches, 130.140.150, 16 (+, 212,
222, 232, 242, the optical bistable element 700 is an optical branch circuit, and 760 is an optical input circuit. Figure 7f OPc PbF 1, 1, 1

Claims (1)

[Claims] (1; A control circuit between an input optical waveguide for inputting the first time-division multiplexed optical signal and an output waveguide for outputting the second time-division multiplexed optical signal. and a plurality of optical bistable elements injected with bias light, respectively, and the control circuit for the first time-division multiplexed optical signal, thereby controlling the input optical waveguide to transmit the plurality of light beams in the selected time slot. The time selected by the control circuit of the bistable element, the first optical switch circuit connected to each input terminal of the selected optical bistable element, and the control circuit of the second time-division multiplexed optical signal. A second optical switch circuit connects the output ends of the optical bistable elements selected by the control circuit of the plurality of optical bistable elements to the output optical waveguide in the slot, and the plurality of optical bistable elements are controlled by the control circuit. and means for reducing the bias light of the optical bistable element selected by the control circuit of the bistable element to a predetermined amount of light or less. (2) A first Between the input optical waveguide for inputting the time division multiplexed optical signal and the output optical waveguide for outputting the second time division multiplexed optical signal, a control circuit, a plurality of optical bistable elements, and a plurality of A plurality of bias lights respectively applied to the input terminals are guided to the input terminals of the plurality of optical bistable elements, respectively, and a time slot I selected by the control circuit of the first time division multiplexed optical signal is Then, the control circuit f of the plurality of optical bistable elements switches the bias light guided by the input terminal of the selected optical bistable element to the first time-division multiplexed optical signal. an optical switch circuit and an output terminal of the optical bistable element selected by the control circuit of the plurality of optical bistable elements in a time slot selected by the control circuit of the second time-division multiplexed optical signal; , and a second optical switch circuit connected to the output optical waveguide.